Papers by Keyword: Yield Ratio

Abstract: The microstructure and mechanical properties of ferritic rolling low carbon steel are investigated by metallurgical microscope, thermal simulation testing machine, electron backscattered diffraction (EBSD) and universal tensile test machine. The finishing temperature of the transition from austenite to ferrite changed from 680°C to740 °C with different cooling rates, which was obvious lower than that of the interstitial free steel. The deformation stress of low carbon steel was larger than that of interstitial free steel. In addition, the deformation stress of the low carbon steel was more sensitive to the deformation rate than that of the interstitial free steel. The microstructure at the surface layer of the hot rolling plate was composed of fully recrystallized grains while the microstructure in the center was composed of fibrous deformed grains. The ferritic rolling low carbon steel has lower yield ratio and higher elongation than that of normal rolling low carbon steel.

Abstract: The effect of finish cooling temperature on microstructure and mechanical properties of X100 pipeline steels were investigated through SEM, TEM and mechanical tests. The results showed that the effect of finish cooling temperature on tensile strength of studied steels were slight in the temperature range of 180°C~500°C. The yield ratio, yield strength and impact toughness all presented peak value when the finish cooling temperature was 360°C, however, both the volume fraction and particle size of MA component at 360°C finish cooling temperature had the minimum values. As a brittle hardening phase in bainite the increased number and enlarged size of the MA component were the key factor of the decrease of the yield ratio and toughness. Therefore, rational choosing finish cooling temperature could optimize the morphology and distribution of MA component to make sure the required strength and toughness for the X100 pipeline steel production.

Abstract: A high deformation pipeline steel X70 with low yield ratio of 74% was achieved has been processed on an industrial scale. The impact toughness of the investigated steel is 388.3 J/cm2 at -20°C and the shear area is 97% in drop weight tear test at -15°C. The microstructure of the steel constisted of primarily acicular ferrite, polygonal ferrite and a small proportion of scattered martensite-austenite constituents. The high deformation pipeline steel had low yield ratio and good toughness, which was attributed to high Nb microalloying and rapid cooling in the TMCP process.

Abstract: The microstructures have been investigated in steel plates with different rolling processes to find the reasons of yield ratio overseted standard in few high strength building steel plates produced in Echeng Iron and Steel Corporation. The effects of rolling path, rolling path depress ratio on microstructure and properties. Some reasons of yield ratio overseted standard have been analyzed. The results show that decreasing rolling paths and increasing depress ratio refined grains but unchanged area ratio and interlamellar spacing of pearlite. Yield strength excessively increased but tensile strength unchanged increased yield ratio. So, excellent properties can be obtained by applying the optimization process.

Abstract: The influence of tempering temperature on the microstructure and mechanical properties of low carbon low alloy steel was investigated. The results show that tempering temperature has considerable influence on both yield strength and tensile strength. With the increase in tempering temperature, the yield strength increases first and then decreases after it reaches the highest point at 600°C with a strength of 843MPa, while the tensile strength decreases fastly from 550°C to 650°C and keeps stable after increasing drastically at 720°C. The yield ratio is about 0.60 except at 600°C and 650°C with a high yield ratio of 0.90, while the total elongation has little change. It is concluded that the major change of mechanical properties after tempering has a connection with the decomposition of M/A(martensite/austenite) islands, the recovery of dislocations and the precipitation of alloy elements.

Abstract: In high strength pipeline steel rolling technology, the control of final cooling temperature of different microstructure, different microstructure of pipeline steel tensile strength, yield strength and the effects of different, thus determine its yield ratio differences. The results show that with lath bainite microstructure of the pipeline steel than with acicular ferrite microstructure of the pipeline steel with lower yield ratio, at the same time lath bainite microstructure in small dispersed precipitates in pipeline steel X80 pipeline steel to reduce the yield ratio is beneficial, for high strength pipeline steel production technology to provide the theory basis.

Abstract: The nominal yield ratio, true yield ratio and static toughness of five materials X80, X65, X60, X46 and Q235 have been tested in this paper. The yield ratio of pipeline steel is rising with the increase of strength level, which is inevitable for the high strength pipeline steel. Based on the analysis of static toughness calculated by the true stress-strain curve, it is indicated that the deformation energy of X80 pipeline steel after the necking process in the course of static tension is high comparatively, and the deformation energy of X80 pipeline steel before the necking process is closed to that of the pipeline steel X46 and X60 with low yield ratio. It is showed that the increase of yield ratio did not lead to the decline of the static toughness.

Abstract: To develop 590/780MPa grade low yield ratio structural steel, the effects of ultra fast cooling (UFC) new process on microstructure and mechanical properties were investigated. The results showed that the low yield ratio and high strength can be obtained by proper phase compositions including relative soft phase and hard phase. For the process of UFC + air cooling, when UFC final cooling temperature was 521°C, 22.5% M-A second hard phases were distributed on bainite ferrite matrix in steel No.A2. The mechanical properties can meet requirement of 590MPa grade low yield ratio structural steel. For the process of air cooling + UFC, when UFC initial cooling temperature was 781°C, the multiphase composed of 28.3% ferrite and other bainite / martensite lath structure can ensure the high strength and low yield ratio of steel No.B1. And performance indexes can meet the requirement of 780MPa grade low yield ratio structural steel.

Abstract: High strength steel plates with 780MPa in tensile strength, suitable for building construction use, have been developed. The steel plates provide excellent combination of high strength, toughness, deformability and weldability. The key technology to obtain the excellent combination in mechanical properties of the steel is the microstructural control of M-A (martensite-austenite constituent) and the bainitic ferrite dual-phase structure, through the on-line heat treatment immediately after the accelerated cooling in Thermo-mechanical control process (TMCP). The developed steel plates have microstructure of fine M-A dispersed in the bainitic ferrite matrix. Basic metallurgical research revealed that the transformation behavior and microstructural morphologies were varied with the cooling stop temperature before the on-line heating, and the on-line heating temperature itself. Trial production of the developed 780MPa grade steel plates was also carried out with the plate mill. The obtained plates showed the satisfactory combination of high strength, low yield ratio, toughness.

Abstract: The environmentally friendly manufacturing process, continuous casting process with small cross sections, is the near net-shaped manufacturing technology used to fabricate copper alloy wires and plates with the required final tolerance and sound quality. Furthermore, the process consumes less energy and discharges less environmental loads because the process can eliminate the need for hot extrusion, hot rolling and heat treatment for production copper alloy wires and plate. In the present study, the effects of a continuous casting speed on the mechanical properties and the microstructure of the nickel-silver (Cu-Ni-Zn) alloy were studied and energy requirements, atmospheric CO2 emission and yield for the production of the Cu-Ni-Zn alloy was investigated quantitatively with respect to continuous casting with small cross sections and conventional material processing including casting, extrusion and heat treatment. The yield for production of Cu-Ni-Zn alloy can be improved above 30% with the application of continuous casting with small cross sections when the productivity is similar. Twice the amount of energy required and CO2 were consumed and emitted in the conventional manufacturing process when the yield of the processes was considered.